A list of helpful libraries and code

Based on a conversation in the Playdate Squad Discord earlier I came up with some functions for drawing bezier curves in the Playdate Lua SDK by using line segments. Both quadratic beziers (3-point) and cubic beziers (4-point, the kind you'd find in most vector drawing apps) are supported!

This site has a nice interactive demo to compare both kinds of curves and the step parameter: A Primer on Bézier Curves

6 Likes

I'll add this here too in case the announcement thread falls by the way side. I'm working on a little Amiga mod player, blast from the past but could be very useful given the memory constraints if we can get it to run fast enough on real hardware.

2 Likes

You may want to check for overflow when implementing calloc. It's one of the reason it's best to use calloc versus malloc with a total size to avoid buffer overruns (although on PlayDate it probably will not be an issue given the lack of user input on these calls).

Something like this:

void* pd_calloc(size_t nb_of_items, size_t item_size)
{
    if (item_size && (nb_of_items > (SIZE_MAX / item_size))) {
        return NULL;
    }

    size_t size = nb_of_items * item_size;
    void* memory = pd_malloc(size);
    if(memory != NULL) {
        memset(memory, 0, size);
    }
    
    return memory;
}

I built a dependency/package manager for Playdate: https://github.com/jm/toybox Just got the binary releases up (accessible at Release First release! · jm/toybox · GitHub) so I hope folks can give it a spin. I'm working on getting it published in package managers etc so it's easier to upgrade.

I also published a repo of examples for things that don't currently have single file examples so that they have focused example scripts to learn from: https://github.com/jm/playdate_examples I'll be adding to this as I experiment with more of the APIs for sure. :slight_smile:

6 Likes

Amazing! I'm working on a little eurorack modular synth app for the Playdate, but I love trackers. My Polyend Tracker is my fav piece of gear!

8 Likes

Mentioned in a discussion thread I created, but wanted to drop this here in case it's useful to anyone checking this thread in the future. I started work on a tool to more easily view and choose dither patterns directly on device:

Thanks!

2 Likes

Show Toast message (temporary text that pop up on the screen) code:

local function showToast(text, duration)
    local t = playdate.frameTimer.new(duration)
    t.updateCallback = function()
        Graphics.drawTextAligned(text, 200, 70, kTextAlignment.center)
    end
end

Feel free to change text position (200, 70)

8 Likes

I love how simple and useful it is.
Really nice function!

1 Like

Here's a function I wrote to draw an image tiled within bounds with an optional offset. The built-in image:drawTiled(...) does not take a draw offset, so the tiled image is always tiled from 0, 0 of the destination rect. Ehh, it appears to work! :wink:

function drawTiledImage(img, bounds, offset_x, offset_y)
	offset_x = offset_x or 0
	offset_y = offset_y or 0

	-- Take easy route when no offset is specified.
	if offset_x == 0 and offset_y == 0 then
		img:drawTiled(bounds)
		return
	end

	local iw, ih = img:getSize()
	local sx = math.abs(offset_x % iw) - iw + bounds.x
	local sy = math.abs(offset_y % ih) - ih + bounds.y
	
	local cx, cy, cw, ch = playdate.graphics.getClipRect()
	playdate.graphics.setClipRect(bounds)
	img:drawTiled(sx, sy, bounds.width - sx, bounds.height - sy)
	playdate.graphics.setClipRect(cx, cy, cw, ch)
end
1 Like

Converted the Roomy scene manager lib over to be useable with playdate

github

::edit::
Finally added a read me :stuck_out_tongue:

7 Likes

Here's a simple class I made to make a scrolling parallax background simple

local pd <const> = playdate
local gfx <const> = pd.graphics

class("Parallax").extends(gfx.sprite)

function Parallax:init()
 Parallax.super.init(self)
 self.layers = {}
end

function Parallax:draw(...)
 gfx.setClipRect(...)
 for _, layer in ipairs(self.layers) do
   local img = layer.image
   -- lock offset to steps of 2 to reduce flashing
   local offset = layer.offset - (layer.offset % 2)
   local w = layer.width
   img:draw(self.x+offset, self.y)
   if offset < 0 or offset > w - self.width then
     if offset > 0 then
       img:draw(self.x+offset-w, self.y)
     else
       img:draw(self.x+offset+w, self.y)
     end
   end
 end
 gfx.clearClipRect()
end

function Parallax:addLayer(img, depth)
 local w, _ = img:getSize()
 local layer = {}
 layer.image = img
 layer.depth = depth
 layer.offset = 0
 layer.width = w
 table.push(self.layers, layer)
end

function Parallax:scroll(delta)
 for _, layer in ipairs(self.layers) do
   layer.offset = math.ring(
     layer.offset + (delta * layer.depth),
     -layer.width, 0
   )
 end
 self:markDirty()
end

it also uses the math.ring function that was posted is this thread somewhere (I can't find it atm)

function math.ring(a, min, max)
  if min > max then
    min, max = max, min
  end
  return min + (a-min)%(max-min)
end

It's simple to use:

img_1 = gfx.image.new("images/parallax-1")
img_2 = gfx.image.new("images/parallax-2")

-- create
local parallax = Parallax()
parallax:setSize(400,240)
parallax:addLayer(img_1, 0.2)
parallax:addLayer(img_2, 0.6)
parallax:add()

-- scroll
parallax:scroll(10)

parallax

8 Likes

Pulled code from Lua SDK to read cranks ticks and wrapped it in an object. The reason for this is that the SDK code uses a local global vars which can be an issue if you want to read the number of ticks, or even with a different ticksPerRevolution value. Each reading resets the sampler.

So, with this code you simply create a Ticker, and sample each frame or whatever. You can reset it too during periods where you don't need samples.

You can of course create multiple Tickers each with their own ticksPerRevolution values to sample at different rates.

local ticker = Ticker.new(20)

-- elsewhere:

function update()
   local ticks = ticker:sample()
end

Anyway, I've found it helpful so thought you may too.

Ticker = {}
Ticker.__index = Ticker

function Ticker.new(ticks_per_revolution)
	local ticker = {}
	setmetatable(ticker, Ticker)
	
	ticker.ticks_per_revolution = ticks_per_revolution
	ticker.last_reading = nil
	
	return ticker
end

function Ticker:setTicksPerRevolution(ticks_per_revolution)
	self.ticks_per_revolution = ticks_per_revolution
end

function Ticker:reset()
	self.last_reading = nil
end

function Ticker:sample()
	local totalSegments = self.ticks_per_revolution
	local degreesPerSegment = 360 / self.ticks_per_revolution
	
	local thisCrankReading = playdate.getCrankPosition()
	local lastCrankReading = self.last_reading
	if lastCrankReading == nil then
		lastCrankReading = thisCrankReading
	end
	
	-- if it seems we've gone more than halfway around the circle, that probably means we're seeing:
	-- 1) a reversal in directiotn, not that the player is really cranking that fast. (a good assumption if fps is 20 or higher; maybe not as good if we're at 2 fps or similar.) 
	-- 2) a crossing of the 359->0 border, which gives the appearance of a massive crank change, but is really very small.
	-- both these cases can be treated identically.
	local difference = thisCrankReading - lastCrankReading
	if difference > 180 or difference < -180 then
		
		if lastCrankReading >= 180 then
			-- move tick_lastCrankReading back 360 degrees so it's < 0. It's the same location, just it is unequivocally lower than thisCrankReading
			lastCrankReading -= 360
		else
			-- move tick_lastCrankReading ahead 360 	degrees so it's > 0. It's the same location, just now it is unequivocally greater than thisCrankReading.
			lastCrankReading += 360
		end
	
	end
	
	-- which segment is thisCrankReading in?
	local thisSegment = math.ceil(thisCrankReading / degreesPerSegment)
	local lastSegment = math.ceil(lastCrankReading / degreesPerSegment)
	local segmentBoundariesCrossed = thisSegment - lastSegment
	
	-- save off value
	self.last_reading = thisCrankReading
	
	return segmentBoundariesCrossed	
end
2 Likes

Determine tilt angle from reference point using accelerometer.

Spent a bit of time trying to figure this out so thought I'd just share here. If you want to determine the angle a player has tilted the device vertically (along the Y), I've so far found this to work pretty well:

-- Store reference position which to measure tilt from.
local _, ay, az = playdate.readAccelerometer()
local start_v = geometry.vector2D.new(ay, az)

-- Elsewhere, measure angle off reference position
local _, ay, az = playdate.readAccelerometer()
local current_v = geometry.vectory2D.new(ay, az)
local tilt_angle = start_v:angleBetween(current_v)

I think that's it. Though I haven't tried it, it seems you'd be able to measure tilt along the X axis by replacing ay with ax (the first value off readAccelerometer that I'm ignoring in this example).

OK! Happy, um, accelerating?

7 Likes

Cheat Codes

I've been working on adding some cheats to my game, figured I'd share the class here incase anyone else would like it.

local keys = {
  a = playdate.kButtonA,
  b = playdate.kButtonB,
  up = playdate.kButtonUp,
  down = playdate.kButtonDown,
  left = playdate.kButtonLeft,
  right = playdate.kButtonRight
}

class("CheatCode").extends()

function CheatCode:init(...)
  local seq = {}
  for _, key in ipairs({...}) do
    local v = keys[key]
    assert(v, "CheatCode: unknown key given => "..tostring(key))
    table.insert(seq, v)
  end

  self._seq = seq
  self.progress = 1
  self.completed = false
  self.run_once = true
  self:setTimerDelay(400)
end

function CheatCode:update()
  -- exit early if complete
  if self.run_once and self.completed then return end

  local _, pressed, _ = playdate.getButtonState()
  -- exit early if no button currently pressed
  if pressed == 0 then return end

  if pressed == self._seq[self.progress] then
    self.progress += 1
    self._timer:reset()

    if self.progress > #self._seq then
      self.completed = true
      if type(self.onComplete) == "function" then
        self.onComplete()
      end
    end
  else
    self:reset()
  end
end

function CheatCode:reset()
  self.progress = 1
  self._timer:reset()
  self._timer:pause()
end

function CheatCode:setTimerDelay(ms)
  if self._timer then
    self._timer:remove()
  end
  self._timer = playdate.timer.new(ms, function() self:reset() end)
  self._timer:pause()
  self._timer.discardOnCompletion = false
end

function CheatCode:nextIs(key)
  return keys[key] == self._seq[self.progress]
end

Using it is simple enough

-- initialize 
local cheat = CheatCode("up", "up", "down", "down", "left", "right", "left", "right", "b", "a")
cheat.onComplete = function() print("cheat") end
-- in update function
playdate.timer.updateTimers() -- uses timers so make sure you call this
cheat:update()

By default it'll only trigger the first time the sequence is called, can be changed by setting run_once to false

CheatCode:nextIs([key]) is a helper to allow you to avoid triggering other effects while the code is being entered. eg:

if not cheat:nextIs("a") then
    -- do something else
end
5 Likes

This is very helpful! Have you put this in a github repo with some documentation by any chance?

@dustin , I am quite interested in using this model as it could make reusing some cutscenes or parts of them quite easy (probably in conjunction with the Sequence lib also posted on the page here).
Nonetheless, could you clarify where does the dt param come from in your example? I assume it means time difference, but I am a bit confused by it.

I am hoping to achieve nicer animations on cutscenes with the use of these 2 libs, but please let me know if there is an easier way :slight_smile:
Thanks for the help

The easiest way to calculate the time delta between frames is just to assume it's the current frame rate. You could just use:

local dt <const> = 1.0 / playdate.display.getRefreshRate()

Or if you want to be more accurate, you could do something like:

local previous_time = nil
function playdate.update()
	local dt = 0
	local current_time <const> = playdate.getCurrentTimeMilliseconds()
	if previous_time ~= nil then
		dt = (current_time - previous_time) / 1000.0
	end
	previous_time = current_time
	if dt == 0 then
		return
	end
end
2 Likes

Simple just works object pooling function.

---Add objectToAdd into list
---@param list table table list
---@param objectToAdd table needs a "enabled" key
function ObjectPooling(list, objectToAdd)
	local found = false

	for i = 1, #list, 1 do
		local o = list[i]
		if not o.enabled then
			
			list[i] = objectToAdd
			found = true

			break
		end
	end

	if not found then
		list[#list+1] = objectToAdd
	end
end
1 Like

Super simple function to shake the camera multiple times, defined by _numberOfShakes, waiting _delayBetweenShakes milliseconds between each shake. The amount the camera moves each shake is a random number of pixels between -_offsetAmount and _offsetAmount.

Example - When my player takes damage, I just call this function:
cameraShake(20,15,3)

Note: This does use the PlaydateSDK Timer, so remember to call playdate.timer.updateTimers() in your playdate.update() function.

function cameraShake(_numberOfShakes,_delayBetweenShakes,_offsetAmount)
    -- do some shakes
    for i = 1, _numberOfShakes do
        playdate.timer.performAfterDelay(i*_delayBetweenShakes, function()
            playdate.graphics.setDrawOffset(math.random(-_offsetAmount,_offsetAmount),math.random(-_offsetAmount,_offsetAmount))
        end)
    end

    -- reset camera
    playdate.timer.performAfterDelay(_numberOfShakes*_delayBetweenShakes+_delayBetweenShakes, function()
        playdate.graphics.setDrawOffset(0,0)
    end)
end
1 Like

There was a post about this earlier in this thread but since we have some updates regarding the project, I'll link to the announcement thread here too.

A lot of the code posted here could greatly benefit being shared via a toybox which makes is easy to install, maintain and update. Even single methods can be shared as single file toyboxes providing very targeted functionality but allowing everyone to easily use or contirbute to the toybox.

It would be wonderful to have this wealth of libs we can all use to get any project up and running quicker.

More info: (re?)-Introducing toybox.py - A Dependency Manager for the Playdate

If you need help creating or using a toybox for your stuff, please reach out directly to me and I will help you out.

1 Like